May 2017

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May 2017

Average surface air temperatures for May 2017

Surface air temperature anomaly for May 2017 relative to the May average for the period 1981-2010. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service) Download the original image

May 2017 was warmer than the 1981-2010 average over the west of Europe, especially over Portugal and Spain. Temperatures were considerably below average over the north-east of the continent.

Temperatures were most above average over and offshore of West Antarctica, where sea-ice cover was unusually low for the time of year. Parts of east Antarctica also had temperatures that were substantially above average. The Canadian Arctic, Greenland, north-western Africa and central Asia also experienced much above-average temperatures. Below-average temperatures extended from north-eastern Europe to northern Siberia, and also occurred over a sector of the Arctic Ocean around and north of Svalbard that has generally experienced above-average temperatures in recent months and years.

Temperatures were predominantly above average over the oceans. Cold values south of Newfoundland appear linked to cold sea-surface temperatures associated with a southward extension of the Labrador Current.

Surface air temperature anomaly for June 2016 to May 2017 relative to the average for 1981-2010. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service) Download the original image

Average temperatures for the twelve-month period from June 2016 to May 2017 were:

most above the 1981-2010 average in the Arctic;

higher than average over most areas of land and ocean;

lower than average mainly over parts of the southern oceans and a few land areas;

lower than average also over the equatorial Pacific, where weak La Niña conditions prevailed until early 2017.

Monthly global-mean and European-mean surface air temperature anomalies relative to 1981-2010, from January 1979 to May 2017. The darker coloured bars denote the May values. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service)Access to data Download the original image

May 2017 extended the spell of exceptional global warmth that has now lasted since mid-2015. Although the global temperature anomaly peaked in February 2016 and declined steadily until June that year, it rose again in July and August, and has remained high since. May 2017 was:

0.56OC warmer than the average May from 1981-2010;

the second warmest May on record;

0.03OC cooler than May 2016.

Only three months from October 2015 onwards have been less extreme than January 2007, which was previously the month with the highest anomaly (0.54OC). The warmest instances of each month of the year occurred from October 2015 to September 2016, and each of the eight months since then has been the second warmest on record for that month of the year.

The largest anomalies in European-average temperatures occur in wintertime, when values can vary substantially from month to month. The average for Europe in May 2017 was very close to the 1981-2010 norm.

Running twelve-month averages of global-mean and European-mean surface air temperature anomalies relative to 1981-2010, based on monthly values from January 1979 to May 2017. The darker coloured bars are the averages for each of the calendar years from 1979 to 2016. Source: ERA-Interim. (Credit: ECMWF Copernicus Climate Change Service)Access to data Download the original image

Averaging over twelve-month periods smooths out the shorter-term variations. Globally, the twelve-month average from June 2016 to May 2017 is 0. 57°C above the 1981-2010 average. The warmest twelve-month period on record is from October 2015 to September 2016, with a temperature 0.64°C above average. 2016 is by far the warmest calendar year on record: its global temperature of 0.62°C above the average for 1981-2010 compares with values of 0.44°C and 0.35 °C respectively for 2015 and 2005, the two next warmest calendar years.

The spread in the global averages from various temperature datasets has been unusually large in recent months, due to differences in the extent to which datasets represent the relatively warm conditions that have predominated over both the Arctic and the Antarctic. Spread is also high for the year 2005. Nevertheless, there is general agreement between datasets regarding:

the exceptional warmth of 2016, and to a lesser extent 2015;

the overall rate of warming since the late 1970s;

the sustained period of above-average temperatures from 2001 onwards.

There is more variability in average European temperatures, but values are less uncertain because observational coverage of the continent is relatively dense. Twelve-month averages for Europe were at a high level from 2013 to 2016. They have fallen in recent months, but remain well above the 1981-2010 average. The warmest twelve-month period occurred from July 2006 to June 2007.